The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Within the motor vehicle automatic transmission art, the dual clutch transmission (DCT) is a relative newcomer. A typical dual clutch transmission configuration includes a pair of mutually exclusively operating input clutches which drive a pair of layshafts or countershafts disposed on opposite sides of an output shaft. One of each of a plurality of pairs of constantly meshing gears which define the various forward gear ratios is freely rotatably disposed on one of the layshafts and the other of each pair of gears is coupled to the output shaft. A like plurality of synchronizer clutches selectively couple one of the gears on the layshaft to the layshaft to achieve a forward gear ratio. After the synchronizer clutch is engaged, the input clutch associated with the active layshaft is engaged. Reverse gear is similarly achieved except that it includes an extra gear to provide torque reversal.
Dual clutch transmissions are known for their sporty, performance oriented characteristics. They typically exhibit good fuel economy due to good gear mesh efficiency and ratio selection flexibility. The synchronizer clutches have low spin losses which also contributes to overall operating efficiency.
However, dual clutch transmissions have several unique design considerations. For example, because of the heat that can be generated during slip, the input clutches must be of a relatively large size. Furthermore, such heat generation typically requires correspondingly large and complex cooling circuits capable of dissipating relatively large quantities of heat. Finally, because such transmissions typically have many sets of axially aligned, intermeshing gears, their overall axial length may limit their use in some vehicle designs.
One alternative to utilizing only a pair of input clutches in a dual clutch transmission to achieve launch and torque throughput control is to incorporate a torque converter. While such an addition to a dual clutch transmission simplifies launch considerations and can reduce the required torque capacity and size of the input clutches, it may have an adverse impact on performance and fuel economy. Due to the additional complexity of the device, improving the performance and fuel economy of a dual clutch transmission having a torque converter presents a challenge. The challenge is addressed herein with an invention directed to a control system for a dual clutch transmission having a torque converter.